Use native resolution for this game. I have the ntsc version of this game and get 60 fps for the most part. It will drop to 45-50 fps just before the race starts and for the first 3-5 seconds of the race. I get about the same speed whether i'm using hardware or software mode for this game.

That video card is relatively weak for gaming. You're getting a higher framerate initially because the menus and videos aren't demanding on the 3D hardware, whereas the actual game is. If you could upgrade your video card, it would perform much better.